diff --git a/addons/website_sale/controllers/main.py b/addons/website_sale/controllers/main.py
index 283c37a4abd..e3e4a105f82 100644
--- a/addons/website_sale/controllers/main.py
+++ b/addons/website_sale/controllers/main.py
@@ -1046,16 +1046,21 @@ class WebsiteSale(http.Controller):
         return partner_id
 
     def values_preprocess(self, values):
-        """ Convert the values for many2one fields to integer since they are used as IDs.
-
-        :param dict values: partner fields to pre-process.
-        :return dict: partner fields pre-processed.
-        """
+        new_values = dict()
         partner_fields = request.env['res.partner']._fields
-        return {
-            k: (bool(v) and int(v)) if k in partner_fields and partner_fields[k].type == 'many2one' else v
-            for k, v in values.items()
-        }
+
+        for k, v in values.items():
+            # Convert the values for many2one fields to integer since they are used as IDs
+            if k in partner_fields and partner_fields[k].type == 'many2one':
+                new_values[k] = bool(v) and int(v)
+            # Store empty fields as `False` instead of empty strings `''` for consistency with other applications like
+            # Contacts.
+            elif v == '':
+                new_values[k] = False
+            else:
+                new_values[k] = v
+
+        return new_values
 
     def values_postprocess(self, order, mode, values, errors, error_msg):
         new_values = {}
@@ -1152,7 +1157,7 @@ class WebsiteSale(http.Controller):
                             (not order.only_services and (mode[0] == 'edit' and '/shop/checkout' or '/shop/address'))
                     # We need to update the pricelist(by the one selected by the customer), because onchange_partner reset it
                     # We only need to update the pricelist when it is not redirected to /confirm_order
-                    if kw.get('callback', '') != '/shop/confirm_order':
+                    if kw.get('callback', False) != '/shop/confirm_order':
                         request.website.sale_get_order(update_pricelist=True)
                 elif mode[1] == 'shipping':
                     order.partner_shipping_id = partner_id